* fix: parse Claude.ai privacy export with messages key and sender field (#677)
The privacy-export branch in _try_claude_ai_json only checked for the
"chat_messages" key, missing exports that use "messages" instead. It
also only read the "role" field while real privacy exports use "sender".
Both gaps caused the file to fall through to plain-text, producing a
single giant drawer.
Changes:
- Accept "messages" alongside "chat_messages" in the conversation-object
guard and inner extraction.
- Accept "sender" alongside "role" as the author field.
- Fall back to a top-level "text" key when content blocks are empty.
- Produce one transcript per conversation instead of concatenating all
conversations into a single blob.
- Extract shared logic into _collect_claude_messages helper.
- Add 6 regression tests covering each variant.
* style: apply ruff format to normalize.py
* fix: guard against null text field in Claude.ai export parsing
item.get("text", "").strip() crashes when "text" is explicitly null
in the JSON (legal and observed in some exports). Use
(item.get("text") or "").strip() and add a regression test.
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Co-authored-by: Igor Lins e Silva <4753812+igorls@users.noreply.github.com>
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